Even though the conventional technologies of optical lithography are currently most widely employed for high-volume production of microelectronic components and can provide great advantages because the high throughput achieved through the parallel processes of nature pattern generation, however, the lithographic technologies still have several limitations and drawbacks. In order to overcome such limitations and drawbacks, various maskless lithographic technologies have been explored and disclosed. Particularly, as will be further discussed below, various patented inventions have been attempted to improve the efficiency and performances of the markless lithographic technologies.
However, such technologies still have difficulties that the conventional systems are limited to either horizontal or vertical overlapping of scanning exposures but not two-dimensional exposure overlaps while maintaining seamless exposure patterns. Stringent moving direction control with tight limitations of tolerance must be maintained because such single direction overlapping limitations. Furthermore, as technologies progress, there are greater demands of higher resolution control to achieve higher level of uniformity of exposures. Conventional technologies applying spatial light modulation (SLM) have difficulties in satisfying these requirements, especially those SLM that implemented with micromirrors due to the limited degree of controllability of light reflected from each micromirror. Additionally, the throughput of the lithographic operations are limited as higher rate speed of data transmission is required to adjust the lithographic exposures and conventional technologies usually do not have sufficient data transfer rates to satisfy these requirements. Last but not least, the level of contrast for exposures as that provided by conventional technologies are still limited that further limit the quality and performance and quality of semiconductor manufacturing processes to produce integrated circuits with ultra-high cell density with precise controlled critical dimensions while maintaining very tight misalignment tolerances.
Varieties of factors still exist in the lithographic technologies that can significantly reduce the manufacturing speed and efficiency. Specifically, the speed of a single exposure is often determined by the intensity of the illumination and the sensitivity of the resist. Efforts are devoted to improve the exposure speed by increasing the illumination intensity and/or the resist sensitivity. However, for circuits especially those with many layers of feature, require many individual exposures. Operations to switch the masks between exposures often cost a significant amount of overhead in manufacturing throughput. Furthermore, a mask has to be accurately placed to satisfy the alignment requirements. Throughput is further reduced through such operations. Production costs are further increased due to the requirement that a fabrication facility of microelectronic components often has to have an inventory of different masks to generate wide varieties of patterns. The inventory further increases the overhead of manufacturing the integrated circuits and the costs and time are further added by processes and time required to order such masks.
In addition to above factors, the demand for developing maskless lithography is further increased as the cost the mask is tremendously increased with increase of size and reduced pitch between the microelectronic structural features. Meanwhile, the increased integrations of functions and the miniaturization of electronic devices, further push these trends to produce masks with larger areas with small pattern pitches that lead to very expensive masks required for electronic device manufactures. For these reasons, it would be of great value to provide maskless lithographic technologies to overcome these limitations and difficulties.
Several recent patented disclosures are made in the field of maskless lithography that include U.S. Pat. No. 6,238,852 that discloses the applications of light projected to two directions so that two substrates can be exposed simultaneously. The lithography process is performed by a maskless lithography system that provides large-area, seamless patterning using a reflective spatial light modulator such as a Deformable Micromirror Device (DMD) directly addressed by a control system so as to provide a first pattern, via a first projection subsystem, on a first photoresist-coated substrate panel, while simultaneously providing a duplicate pattern, which is a negative of the pattern on the first substrate panel, via a second projection subsystem, onto a second photosensitive substrate panel, thus using the normally-rejected non-pattern “off” pixel radiation reflected by the “off” pixel micromirrors of the DMD, to pattern a second substrate panel. Since the “off” pixel reflections create a pattern which is complementary to the “on” pixel pattern, using a complementary photoresist coating on the second substrate panel provides for a duplicate pattern, as is usually desired. Since both the “on” and “off” reflections are used from each pixel position, using the same selection, the result is the doubling of throughput.
Another maskless lithographic system is disclosed in U.S. Pat. No. 6,379,867, a photolithography system and method for providing a mask image to a subject such as a wafer is provided. The mask images are divided into sub-patterns and sequentially provided to a pixel panel, such as a deformable mirror device or a liquid crystal display. The pixel panel converts each sub-pattern into a plurality of pixel elements. Each of the pixel elements is then simultaneously focused to discrete, non-contiguous portions of the subject through a microlense array. The subject and pixel elements are then moved (e.g., one or both may be moved) and the next sub-pattern in the sequence is provided to the pixel panel. As a result, light can be projected on the subject, according to the pixel elements, to create a contiguous image on the subject.
U.S. Pat. No. 6,304,316 further discloses a projection microlithography system that can pattern very large, curved substrates at very high exposure speeds and any desired image resolution, the substrates being permitted to have arbitrary curvature in two dimensions. The substrate is held rigidly on a scanning stage, on which is also mounted a mask containing the pattern to be formed on the substrate. The mask is imaged on the substrate by a projection subsystem, which is stationary and situated above the scanning stage. The mask is illuminated with a polygonal illumination beam which causes a patterned region of similar shape to be imaged on the substrate. Different regions of the substrate are moved in a direction parallel to the direction of the optical axis at the substrate (z-axis) by suitable amounts to keep the segment being exposed within the depth of focus of the imaging lens. The stage is programmed to scan the mask and substrate simultaneously across the polygonal regions so as to pattern the whole mask. Suitable overlap between the complementary intensity profiles produced by the polygonal illumination configuration ensures seamless joining of the scans. This microlithography system includes optomechanical mechanisms for dynamically sensing the substrate height at each point, for moving the substrate in the z-dimension, and/or configuring the focal plane of the projection subsystem so as to always keep the substrate region being exposed within the depth of focus of the projection subsystem.
However, these patented inventions do not provide an effective solutions to the above discussed problems and limitations. Therefore, a need still exists in the art of micro-lithography systems and methods to provide new and improved maskless lithographic systems and processes including those applications to the lithographic equipment for semiconductor manufacturing to provide new and improved methods and systems such that the above-discussed difficulties can be resolved.